The invention relates to a bottom grate of a crusher or drum chipper for chipping and/or comminuting material comprising a stationary body, a rotor mounted rotatably with bearings, the outer circumference of which is provided with crushing and/or cutting blades, and below the rotor with a curved bottom grate conforming to the shape of the rotor, said bottom grate having curved support elements in a direction substantially perpendicular to the axis of the rotor and blades substantially parallel to the direction of the axis. The invention also relates to a method of producing the bottom grate according to the invention.
Most preferably the invention relates to a crusher or drum chipper for reducing the size of pieces of wood-based materials such as logging residues, stubs, bark, waste wood, said device having a rotary rotor provided with blades and a bottom grate for defining the size of the pieces of material. In this patent application the device according to the invention is referred to as crusher without limiting the invention thereto. The device can also be used in other objects, such as e.g. for comminuting demolition waste of municipal waste. For e.g. drying of the material a uniform piece size is important, since uniform piece size produces a uniform drying result.